The scope of this proposal involves the exploration and characterization in vivo and in vitro immunological and other mechanisms effective in the rejection of transplantable tumors in syngeneic animals following treatment with killed Corynebacterium parvum. The study is also designed to evaluate the efficacy of combined immunochemotherapy of incipient metastases in experimental animals using C. parvum vaccine and attempt to delineate the protective mechanisms. The role of macrophages and thymus-dependent lymphocytes (separated from different tissues associated with the reticuloendothelial system) and humoral immunity will be evaluated sequentially during tumor rejection in experimental animals. The plane presented here will also attempt to elucidate the mechanism associated with the prevention of the incidence of spontaneous tumors in high incidence strain mice following C. parvum-mediated tumor rejection. These studies will also attempt to evaluate the efficacy of C. parvum vaccine in the treatment of spontaneous tumors in high incidence strain mice.